Insulin regulation of hepatic glycogen metabolism in the dog.

BISHOP, JONATHAN S., NELSON D. GOLDBERG, AND JOSEPH LARNER. Insulin regulation of hepatic glycogen metabolism in the dog. Am. J. Physiol. 220(Z) : 499-506. 1971.-The effect of insulin on the activity of the glycogen-synthesizing and degrading enzymes was studied in serially collected biopsy samples of dog liver. In intact normal dogs infusion of glucose alone promoted activation of glycogen transferase and inactivation of phosphorylase as readily as did infusion of insulin with glucose. However, in pancreatectomized dogs these enzymic changes were essentially absent when hyperglycemia resulted either from withdrawal of daily insulin or from infusion of glucose when diabetes was “controlled” by daily insulin. A 30-min infusion of insulin into the pancreatectomized dog promoted less activation of transferase (threefold) in the hyperglycemic “diabetic” condition than in the insulin-controlled condition (7to lo-fold). The hepatic concentration of 3’) 5’cyclic AMP in some but not all intact normal and controlled pancreatectomized dogs decreased slightly following insulin infusion, but was not elevated in the diabetic condition. It was concluded that insulin is required for the activation of glycogen transferase in liver.